Mine roof bolt installation



Dec. 29, 1964 J. B. DEMPSEY 3,163,012

MINE ROOF BOLT INSTALLATION Filed Jan. 18, 1961 38 iy gjl l l@ l6 34 l a I2 I E II. 24 f 2 l %ll 32 34 32 34 38 Fig.2

IO Flg 4 ATTORNEYS 3,163,012 ROOF BQLT INSTALLATIOI I Joseph B. Dempsey, 910 Colgate Road, Marietta, Ohio Filed Jan. 18, 1961, Ser. No. 83,539 5 flaims. (CI. 61-45) This invention relates to the art of supporting mine roofs and more particularly to an improved apparatus for supporting mine roofs of the type that are difiicult to hold by the use of conventional mine roof bolt assemblies alone.

The use of mine roof bolt assemblies to support mine roofs without the necessity of timbers or other vertical supports between the bottom and roof has become quite widespread in recent years. An example of a mine roof bolt assembly which is now in widespread commercial use is found in U.S. Patent No. 2,753,750. In brief, the conventional mine roof bolt assembly includes an elongated bolt, usually from four to eight feet long, provided with a head on the lower end thereof and suitable threads on the upper end thereof. The threaded end of the bolt is adapted to receive an expansible anchoring means which, as disclosed in Patent 2,753,750, may comprise a wedge nut threaded to the bolt and engaging opposed segmental shell parts interconnected by a U-shaped bale. In normal operation, the mine roof bolt assembly is inserted, expansible anchoring means end foremost, upwardly through a vertical hole drilled in the roof structure of the mine. Usually the bolt assembly is inserted into the hole by power equipment engageable with the head of the bolt for turning the latter when the assembly has reached the desired position within the hole. The assembly further includes a plate-type washer which is engageable between the head of the bolt and the surface of the roof surrounding the hole. When the bolt is turned by engagement of the power equipment with the head thereof, the anchoring shells are expanded into the wall of the hole and the bolt is tensioned between the expanded anchoring shells and the washer plate so as to retain the stratified material comprising the roof against failure.

In mines having normal mine roof conditions, the roof can be satisfactorily held by installing mine roof bolt assemblies on four-foot centers throughout the extent of the roof. However, where unusual conditions are encountered and difficulties are experienced in holding the roof structure with conventional mine roof bolt assemblies at four-foot centers, it has been the practice heretofore to provide additional support to the roof between the roof bolt assemblies by mounting elongated metal plates between a plurality of aligned adjacent mine roof bolt assemblies. Such a plate may be as long as 16 feet and made out of stock A" thick and having a width of 6". It will be readily appreciated that the use of plates of the size and weight of those indicated above presents many difliculties and hazards in installation, provides an added danger once installed, and materially adds to the cost of holding the roof. Indeed, some mines having highly productive veins have been abandoned solely for the reason that too much expense and danger is involved in the procedures required to hold the roof against collapse. In other words, the cost of providing a safe support for the roof structure in such mines is so great that production of such mines is no longer economically feasible.

An object of the present invention is to provide auxiliary supporting means cooperable with conventional mine roof bolt assemblies to provide added support for mine roof structures of the type which are diflicult to hold with mine roof bolt assemblies alone, which means substantially overcomes the disadvantages of the structures previously employed for this purpose.

United States Patent G ice 3,153,912 Patented Dec. 29, 1964 In general, the present invention is based upon the proposition that the same additional support that was provided by the elongated A" plates previously employed can be provided by relatively thin metal straps or bands of the type employed in strapping together pelletized packages and the like so long as sufiicient tension is applied to the straps during their installation. The invention contemplates a novel procedure for applying such tension.

Another object of the present invention is the provision of apparatus for carrying out the method described above, which apparatus includes strap means for connection with a mine roof bolt assembly and cooperation with similar strap means of adjacent mine roof bolt assemblies so as to be tensioned and secured with respect thereto to thereby provide tensioned support for the mine roof between the positions at which the mine roof bolt assemblies are mounted.

Another object of the present invention is the provision of apparatus of the type described which is simple in construction, economical to manufacture and which can be economically and safely installed.

These and other objects of the present invention will become more apparent during the course of the following detailed description and appended claims.

The invention may best be understood with reference to the accompanying drawings wherein an illustrative embodiment is shown.

In the drawings:

FIGURE 1 is a bottom view of a section of a mine roof showing apparatus embodying the principles of the present invention installed therein;

FIGURE 2 is an enlarged, fragmentary, sectional view taken along the line 22 of FIGURE 1;

FIGURE 3 is an enlarged perspective view of a mine roof bolt assembly washer illustrating one manner in which the straps are connected thereto; and

FIGURE 4 is an enlarged view similar to FIGURE 2 showing a modified form of apparatus.

Referring now more particularly to the drawings, there is shown in FIGURES 1-3 thereof a mine roof, generally indicated at 10, having a plurality of mine roof bolt assemblies, generally indicated at 12, mounted therein in equally spaced relation, as, for example, on four-foot centers. The mine roof bolt assemblies 12 may be of any suitable construction, the embodiment shown being constructed in accordance with the disclosure of Patent No. 2,753,750 mentioned above. Thus, each assembly includes an elongated bolt 14 having a head 16 on the lower end thereof and a wedge nut 18 threadedly mounted on the upper end thereof. The wedge nut 18 forms a part of an expansible anchoring means which also includes a 'pair of segmental cylindrical shell parts 20, each having opposed inclined side edges which diverge upwardly for engagement with opposed downwardly converging wedgmg surfaces oj the wedge nut 18. The shell parts 20 are interconnected by a U-shaped strap or bale 22, which extends upwardly over the wedge nut and upper end of the bolt 14. Each assembly also includes a washer plate 24 having a central aperture 26 formed therein for receiving the bolt 14.

As previously indicated, in the normal operation of the mine roof bolt assemblies 12, the bolt is inserted, anchoring means end foremost, within a vertical hole 28 drilled in the roof 10. When the washer plate 24 engages the surface of the roof 10, the head of the bolt is turned, as by suitable power equipment, which causes the wedge nut 18 to move downwardly along the bolt 14, turning movement of the shell parts being resisted by their initial engagement with the wall of the hole 28. During the downward movement of the wedge nut 18, the shell parts 20 are moved outwardly into the wall of the hole by the engagement of the wedge surfaces of the nut 18 with the inclined side edges of the shell parts 20. In this way, the anchoring means of the bolt assembly is secured within the roof formation and the bolt 14 is tensioned between the anchoring means and the washer plate 24. The roof formation which invariably is in a stratified condition is thus held in such Stratified condition so that failure can not occur.

Under normal conditions, the entire roof of the mine can be safely held by mounting roof bolt assemblies in spaced relation, such as the four-foot center arrangement mentioned above and shown in FIGURE 1. However, the roof conditions are such, in some mines, that added support between the positions at which the mine roof bolt assemblies are mounted is required in ord or to prevent f ailure of the roof To this end, the apparatus of the present invention provides improved strap means, generally indicated at 30 for effecting support of the roof between the mine roof bolt assemblies 12. The strap means 30 preferably comprises metallic strap sections 32. The strap sections are preferably of the type utilized in baling or strapping together industrial packages, such as plywood sheets and the like. The use of such straps in packaging heavy articles for shipment is well-known and there have been developed numerous tools and other equipment for tensioning the straps about the articles and securing the straps in such tensioned condition about the articles. One such system employs the use of metal clips, such as the clip 34, shown in the drawings, which are applied to the overlapping free ends of the strap after the latter have been suitably tensioned and then the clips are crimped, as indicated at 36, to positively prevent any loosening of the securement thus efieoted.

The strap means 30 of the present invention contemplates a strap section 32 suitably secured to the mine roof bolt assembly and having a free end extending outwardly therefrom. Any suitable means may be provided for securing the strap section 32 to the mine roof bolt assembly. For example, a preferred means is shown in FIGURES 1-3 in which a plurality of elongated strapreceiving openings 38 are formed in the plate washer 24 through which one end of the strap section 32 is inserted. This end is then bent over and secured by means of the conventional crimped clip 34, as is clearly shown in FIG- URES 1, 2 and 3.

Each strap section 32 thus secured to each of the mine roof bolt assemblies 12 provides a free end which is cap-ableof being positioned in overlapping relation to the free end of a strap section carried by an adjacent mine roof bolt assembly 12. The overlapping free ends of the strap sections 32 of adjacent mine roof bolt assemblies are then tensioned by moving the free ends in opposite directions away from each other. This tensioning movement preferably is accomplished by conventional tools and other equipment such as are readily commercially available for tensioning conventional metal bands in packaging large articles for shipment. After the ends have been tensioned in overlapping relation they are suitably secured together as by a crimped clip 34. Here again, conventional strap handling equipment may be utilized to effect this operation.

As best shown in FIGURE 2, a sleeve-like plug 49 is mounted on the bolt 14 of the mine roof bolt assembly adjacent the washer piate 24 so as to provide lateral support within the opening 28 her the bolt 14. In this way, the lateral force transmitted to the bolt by the tensioning of the strap section 32 will not cause the bolt to move laterally within the hole in such a way as to interfere with the engagement of the anchoring means therein.

With the arrangement shown in FIGURE 1, the washer plate 24 of the conventional mine roof bolt assembly 12 would be initially produced with one or more of the strap-receiving slots 38. As shown, there are four such slots formed in each plate which enables each bolt assembly to have four strap sections 32 connected therewith.

This arrangement of securing the strap sections 32 to the mine roof bolt assemblies 12 is preferred, since a minimum size strap can be employed. For example, a strap of 1%" wide having a thickness of approximately 5 32" Would be regarded as satisfactory under these conditions and by applying suitable tension between the overlapping end portions of cooperating strap sections secured to adjacent mine roof bolt assemblies and securing the strap sections together under such a tension, a support to the roof 10 between the bolt assemblies is provided which is at least equal to the support pnovided by the utilization of a 6 wide A" plate extending between the bolt assemblies in an untensioned condition.

The tensioning of the strap means between the bolt assemblies provides the same effective holding force to the roof with the use of a light-weight strap as was previously provided with a heavy plate-like untensioned strap. The present arrangement is simple to install in that the straps employed are light in weight and thus more easily handled manually. Moreover, the straps can be secured in the positions desired by the use of conventional strap handling equipment which is readily oommercially available. In addition to the advantages of the present strap means insofar as installation is concerned, there are added advantages in that the costs involved are substantially less than the costs of thick metal plates; and finally, the arrangement presents less hazard after installation.

As indicated above, the strap section 32 may be secured to the mine roof bolt assemblies in any suitable way, the arrangement shown in FIGURES 1, 2 and 3 constituting a preferred embodiment. In FIGURE 4 there is illustrated an alternative procedure for securing the strap sections to the mine roof bolt assembly. In this arrangement, the strap section 32 is provided with an opening 42 through which the bolt 14 of the mine roof bolt assembly extends. The strap is mounted on the mine roof bolt assembly in the manner indicated in FIGURE 4 prior to the insertion of the bolt into the hole, so that after installation of the mine roof bolt assembly the strap section provides two free ends for cooperating in overlapping relation with the free ends of strap sections carried by adjacent mine roof bolt assemblies. In this way a single strap provides two free ends for engagement with two free ends of two adjacent strap sections. While the arrangement shownin FIGURE 4 provides this advantage, it suffers from the disadvantage that the opening 42 weakens the strap and therefore a strap of a wider dimension must be employed in the embodiment shown in FIGURE 4 than in the embodiment shown in FIG- URES 1-3. Of course, more than one strap can be mounted on each bolt.

It will be understood that the arrangement of the present invention is such that the strap sections between adjacent mine roof b olt assemblies can be tensioned and interconnected or alternatively, the strap sections of diagonally disposed mine roof bolt assemblies can be connected. Any desirable pattern can be employed and the straps can be selectively utilized in those areas of the roof where added support is indicated and need not be utilized in those areas where the roof structure is such that the mine roof bolt assemblies alone will provide adequate support.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that the foregoing specific embodiment has been shown and described only for the purpose of illustrating the principles of this invention and is subject to extensive change without departure from such principles. Therefore, this invention includes all modifications encompassed Within the spirit and scope of the following claims.

I claim:

1. A mine roof installation comprising a plurality of mine roof bolt assemblies, each of said assemblies including an elongated bolt extending upwardly into a vertical hole formed in the mine roof, anchoring means on the upper end of said bolt expanded into engagement with the hole, a washer plate having an opening receiving the lower end of said bolt, head means on the lower end of said bolt engaging said washer plate and applying a force thereto urging the same into engagement with the roof adjacent said hole, at least two of said assemblies having elongated relatively thin strap means secured thereto at a position adjacent to and below the roof, each of said strap means including a free end, and means securing the free ends of two of said strap means in overlapping relation with the associated strap means tensioned between the associated assemblies in a position of support beneath the roof.

2. A mine roof bolt installation as defined in claim 1 including a plug means disposed Within the lower end of each mine roof hole and filling the space between the adjacent interior periphery of the hole and the adjacent exterior periphery of the bolt.

3. A mine roof bolt installation as defined in claim 1 wherein each of said strap means is secured to the Washer plate of the associated assembly.

4. A mine roof bolt installation as defined in claim 1 wherein each of said strap means is secured to the bolt of the associated assembly.

5. A mine roof bolt installation as defined in claim 1 wherein said means securing the free ends of two of said strap means comprises a crimped clip.

References Cited in the file of this patent UNITED STATES PATENTS 2,326,481 Meyer Aug. 10, 1943 2,398,130 Beijl Apr. 9, 1946 2,801,522 Kuhn Aug. 6, 1957 2,829,502 Dempsey Apr. 8, 1958 2,849,866 Flygare et a1. Sept. 2, 1958 2,946,473 Moseley July 26, 1960 FOREIGN PATENTS 84,938 Norway Jan. 31, 1955 551,766 Great Britain Mar. 9, 1943 605,996 Great Britain Aug. 4, 1948 808,500 Great Britain Feb. 4, 1959 

1. A MINE ROOF INSTALLATION COMPRISING A PLURALITY OF MINE ROOF BOLT ASSEMBLIES, EACH OF SAID ASSEMBLIES INCLUDING AN ELONGATED BOLT EXTENDING UPWARDLY INTO A VERTICAL HOLE FORMED IN THE MINE ROOF, ANCHORING MEANS ON THE UPPER END OF SAID BOLT EXPANDED INTO ENGAGEMENT WITH THE HOLE, A WASHER PLATE HAVING AN OPENING RECEIVING THE LOWER END OF SAID BOLT, HEAD MEANS ON THE LOWER END OF SAID BOLT ENGAGING SAID WASHER PLATE AND APPLYING A FORCE THERETO URGING THE SAME INTO ENGAGEMENT WITH THE ROOF ADJACENT SAID HOLE, AT LEAST TWO OF SAID ASSEMBLIES HAVING ELONGATED RELATIVELY THIN STRAP MEANS SECURED THERETO AT A POSITION ADJACENT TO AND BELOW THE ROOF, EACH OF SAID STRAP MEANS INCLUDING A FREE END, AND MEANS SECURING THE FREE ENDS OF TWO OF SAID STRAP MEANS IN OVERLAPPING RELATION WITH THE ASSOCIATED STRAP MEANS TENSIONED BETWEEN THE ASSOCIATED ASSEMBLIES IN A POSITION OF SUPPORT BENEATH THE ROOF. 